Its a conversion factor - and its tied back to how C is defined -

"How fast a battery can discharge is it's maximum current capacity. Current is generally rated in C's for the battery. C is how long it takes to discharge the battery in fractions of an hour. For instance 1 C discharges the battery in 1/1 hours or 1 hour. 2 C discharges the battery in ½ or half an hour. All RC batteries are rated in milli Amp hours. If a battery is rated at 2000 mAh and you discharge it at 2000mA (or 2 amps, 1 amp = 1000mA) it will be completely discharged in one hour. The C rating of the battery is thus based on its capacity."

So a 20C rating that would discharge a batt in 3 min (60/20) is another way of looking at discharge. We are generally more interested in the number of amps batt will produce on continuous basis and look at it this way.

So 3700milliamphours/1000 ma/amps * 25C hr = 3.7 *25 = 92.5amps